Stabilized milk products



Patented Feb. 14, 1950 2,491,320 STABILIZED MILK PRODUCTS Daniel K.OLeary, Kennett Square, Pa.,vassignor to E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware NoDrawing.Application February 12, 1946,

' Serial No. 647,209

3 Claims. (01. 99-151) This invention relates to the stabilization ofmilk and milk products and more particularly to their stabilization withsubstituted beta-mercaptopropionic acids or esters. This application isa continuation in part of my U. S. Patent 2,397,976, filed July 25,1942, issued April 9, 1946.

It is known that whole milk and especially dried whole milk develops onstorage an oxidized flavor. This objectionable flavor can be avoided indried whole milk during storage periods up to as much as two yearsdepending upon the method of the preparation of the milk by the additionof certain antioxidizing agents. A number of antioxidizing agents havebeen proposed for this purpose but due inter alia to. their high cost,toxicity, or objectionable flavor, their commercial use has not beenfavored.

An object of the present invention is to provide improved stabilizedmilk and milk products. Another object is to provide agents for milk ormilk products which retard or inhibit their deterioration or prolong theperiod during which an oxidized flavor develops, the agents being freefrom disadvantageous properties of agents herev the invention bystabilizing milk or milk products such as condensed milk, evaporatedmilk, dried milk, cheese, whey, curd, frozen cream, ice cream, butterand butter oil against oxidation by the presence therein of asubstituted 3-mercaptopropionic acid or ester by which-is meantcompounds containing the group ROOCCHiCHzS-X in which R is hydrogen, analkyl, aryl, aralkyl or alicyclic group and in which the monovalentsubstituent X of the sulfur group is a hydrocarbon. The formularepresents such compounds as 3-[Y mercaptolpropionic acid in which Y: isa methyl, ethyl, propyl, butyl, lauryl, phenyl,

I the formation of the oxidized flavor.

z benzyl, naphthyl, (P-methoxy) phenyl, (P-hydroxy) phenyl, eyclohexylgroup or the like; is an oxygenated-hydrocarbon group such ashydroxymethyl, hydroxyethyl, hydroxypropyl, methoxymethyl, ethoxyethyl,or the like; a sulfurhydrocarbon group such as mercaptoethyl,mercaptopropyl, mercaptohexyl or the like; oxygenated-hydrocarbon groupillustrated by the compounds 3-[hydroxymethyl mercaptolpropionic acid(HOOCCI-IzCHzSCHzOH), 3-[hydroxyethyl mercaptolpropionic acid(HOOCCHzCHzSCHzCHzOH) 3-[hydroxypropyl mercaptolpropionic acid(HOOCCHzCHzSCHzCHzCH-iOH) 3-[methoxymethyl mercaptolpropionic acid(HQOCCHzCHzSCHzOCHs) 3- [carboxyethyl mercaptolpropionic acid(HOOCCHzCHzSCHzCHaCOOH) or the like. If the product is to be used forhuman consumption only the non-toxic derivatives are used.

The above hydrocarbon, alcohol, ether, aldehyde, ester, and otherderivatives of S-mercaptopropionic acids are excellent inhibitors of thedevelopment of oxidation flavors as are also the esters. The methyl,ethyl, propyl, butyl, lauryl, myristyl, cetyl, stearyl, and otherstraight, branch chain or cyclic esters may be used.

The inhibitor may be added to the milk in its liquid form or to theproducts made therefrom. It appears to be immaterial whether theinhibitor is added to the milk before or after conversion to theevaporated or dried form for in either case a stabilized product isobtained inhibited against Usually the addition of from 0.05 to 1% ofthe inhibitor is ample to obtain optimum inhibition with a preferredrange between 0.1 and about 0.5%.

The table illustrates the result of stabilizing fluid milk and wholemilk powder by the addition thereto of dialkyl esters of thiodipropionicacid.

Table firt m tiiittiia iifitr Run Treatment changes were noted UntreatedTreated Fluid Milk: Treatments made on milk basis; samples stored at 42g, g me on be V gg gi gfgggg 3;

1 Thiodipropionic acid (or s-lwboxyethyl mercaptolpropionic acid).

It will be noted that with whole milk no oxidaby the presence ofthiodipropionic acid, its esters or the other oxidation inhibitingagents described above. Their utility in this fleld is illustrated bythis example. 50 gallons of milk were treated with about 0.05% dilaurylthiodipropionic acid, the resulting mixture homogenized and then storedat a temperature of 42 F. The resulting homogenized product wasoxidation-free for 72 hours beyond the controls which were oxidized in48 hours.

Butter oil has been stabilized by the direct addition of about 0.03% byweight thereto of thiodipropionic acid and its esters. The result ingproduct was evaluated by the Swift test procedure. Comparative testswere made on a sample containing thiodipropionic acid in the amount of0.10% and one treated with dilauryl thiodipropionic acid present in thesame amount. These samples were compared with a control containing noagent. According to this accelerated stability testing method whichoperates at 99 C. stability values were greater than 115, 105, and 17hours respectively for the acid treated, ester treated, and untreatedproduct. The Swift method is described in "Oil and Soap 10, 105-109(1933) in an article by A. E. King et al., An aceelerated stability testusing the peroxide value 35 3,416,052

as an inde The effectiveness of the agents appears to be general fordairy products whether they are used in solid or liquid tom and theirutility is exemplifled by their ability to maintain the pleasant flavorsand to suppress unpleasant flavors in such food products iorconsiderable periods of time.

I claim:

1. A product of the group consisting of milk, condensed milk, evaporatedmilk, and dried milk to which has been added from 0.05 to 1% by weightof a 3-(mercapto) propionic compound having the linear structuralformula in which R is of the group consisting of hydrogen andhydrocarbon groups and in which the monovalent substituent x is anoxygenated hydrocarbon.

2. Milk to which has been added 0.05 to 1% byiweight 01' a3-carboxyethv1 mercapto propionic ac d.

3. Milk to which has been added 0.05 to 1% by t lgveighi: of a3-carboxyethyl mercapto propionic es r.

DANIEL K. OLEARY.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 2,397,960 Gribbins et a1 Apr. 9,1946 2,397,976 OLeary Apr. 9, 1946 Gribbins Feb. 18, 1947

1. A PRODUCT OF THE GROUP CONSISTING OF MILK, CONDENSED MIL, EVAPORATEDMILK, AND DRIED MILK TO WHICH HAS BEEN ADDED FROM 0.05 TO 1% BY WEIGHTOF A 3-(MERCAPTO) PROPIONIC COMPOUND HAVING THE LINEAR STRUCTURALFORMULA